1. Field of the Disclosure
The present invention relates to a steam generator. More particularly, the present invention relates to a steam generator in a drum-type washing machine having a compact design to facilitate a sealing process and achieve great sealing results.
2. Discussion of Related Art
Generally, laundry devices are home appliances that can perform washing, drying and sterilizing operation on laundry such as various items, fabrics, beddings, clothes or the like. Laundry devices include washing machines, dryers and appliances having both washing and drying functions.
A washing machine may include a pulsator and a tub that are rotated to perform a washing, rinsing, and spinning cycle. More specifically, once wash water and laundry are introduced into the tub and agitated, the washing machine performs washing by using friction force between the wash water and the tub.
Washing machines are often categorized based on the type of method, which is used to perform washing. For example, washing machines can be categorized as a pulsator-type washing machine, an agitating-type washing machine or a drum-type washing machine.
A drum-type washing machine performs washing by rotating a horizontally oriented drum to produce a frictional force between the wash water and the laundry, once detergent, wash water and laundry are introduced into a drum.
Of the three aforementioned types, the drum-type washing machine is often desirable because it consumes less wash water and less detergent than the other types, while reducing damage to the laundry fabrics. Also, the drum-type washing machine washes laundry as if it were scrubbed by human hands, but with less entanglement.
In order to provide a drum-type washing machine that consumes less wash water, studies and efforts have been made in connection with washing of the drum-type washing machine.
Recently, a steam generator is included in the drum-type washing machine to help washing with much less wash water.
In reference to FIGS. 1 and 2, a conventional drum-type washing machine will be described as follows.
A conventional drum-type washing machine includes a body 1, a drum 2, a tub 3 and a steam generator 4. The body 1 defines an exterior of the drum-type washing machine and the drum 2 holds laundry therein. The tub 3 surrounds the drum 2 and the steam generator 4 is installed within the body 1 to produce steam.
An opening 1a is formed in a front surface of the body 1 through which laundry is loaded and unloaded from the drum 2. A door 1b is coupled to the opening 1a and rotates to open and close the opening 1a. 
As shown in FIG. 2, the steam generator 4 includes a steam outlet 4a and a water inlet (not shown), a case 4c, a sheath heater 4d, a water level sensor 4e and a water temperature sensor 4f. The steam outlet 4a and the water inlet are formed in predetermined sides of the steam generator 4. The case 4c holds water and the sheath heater 4d heats the water. The water level sensor 4e senses a water level inside the case 4c. The water temperature sensor 4f senses the temperature inside the case 4c. 
The case 4c includes an upper case and a lower case that are fastened to each other.
Water supplied to the steam generator 4 passes through the water inlet 4b. The water level sensor 4e senses the level of the water so that the steam generator is able to maintain the appropriate amount of water.
The sheath heater 4d heats the water and steam is produced. The steam passes through the steam outlet 4a into the drum 2. The temperature sensor 4f senses the temperature of the sheath heater 4d so that the temperature of the sheath heater 4d can be controlled to be below a predetermined temperature to prevent the sheath heater 4d from over-heating.
However, according to the conventional drum-type washing machine, the sheath heater 4d has a low power density and the size of the sheath heater 4d should be relatively large to produce the amount of steam required for a drum-type washing machine with a large capacity.
As a result, the overall volume of the steam generator 4 is increased in order to accommodate the sheath heater 4d. However, the space necessary to install the steam generator 4 in the body 1 of the washing machine is limited.
Furthermore, if a plate heater is provided to solve this disadvantage, an end portion between the upper case and the lower case and an edge of the plate heater should be separately sealed to prevent water leakage from the case 4c and prevent water from penetrating through a circuit part of the plate heater.
However, such a sealing method is difficult and deteriorates work efficiency.